Closed as not planned
Description
🐛 Bug Report
To Reproduce
Steps to reproduce the behavior:
git clone https://github.com/kentcdodds/jest-save-enter
cd jest-save-enter
npm install
npm run test
Then open the example.test.js and save it a few times until you notice the issue. The test passes, but every now and then, we'll get a console.error from React.
Here's the code in the example.test.js file:
const React = require('react')
const ReactDOM = require('react-dom')
const {act} = require('react-dom/test-utils')
function Comp() {
const [state, setState] = React.useState()
React.useEffect(() => {
setTimeout(() => {
console.log('updating state')
setState('blah')
})
}, [state])
return null
}
test('example', async () => {
const container = document.createElement('div')
// using `act` is required to get effect callbacks run when rendering components
// (React Testing Library does this automatically)
act(() => {
ReactDOM.render(React.createElement(Comp), container)
})
// the `cleanup` function from React Testing Library (which also happens automatically)
// flushes all the in-flight effects by waiting for the next tick of the event loop
// this is basically a simplified version of: https://github.com/facebook/react/blob/master/packages/shared/enqueueTask.js
await new Promise((resolve) => setImmediate(resolve))
// this is the last thing that happens in cleanup (to avoid memory leaks)
ReactDOM.unmountComponentAtNode(container)
}And here's some output:
When it works
Without changing anything, sometimes this happens
Expected behavior
I expect the output to be consistent.
Link to repl or repo (highly encouraged)
https://github.com/kentcdodds/jest-save-enter
This issue is best explained in video form (5 minutes): https://youtu.be/hRxf6QUwkow
envinfo
System:
OS: macOS 10.15.4
CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
Binaries:
Node: 12.13.1 - ~/n/bin/node
Yarn: 1.21.1 - ~/.yarn/bin/yarn
npm: 6.14.5 - /usr/local/bin/npm
npmPackages:
jest: ^26.0.1 => 26.0.1
I honestly have no idea what's going on here, but I definitely observe this happening sometimes in less contrived examples.
Related issues: